#define quickread
#ifdef quickread
#include <cstdio> 
template <typename T>
inline void read(T& x)
{
    int c=getchar(), f=1; x=0;
    while(c<'0'||'9'<c) {if(c=='-') f=-1; c=getchar();}
    while('0'<=c&&c<='9') 
        x=(x<<3)+(x<<1)+c-'0', c=getchar();
    x*=f;
}
template <typename T>
inline void quickwrite(T x)
{
    if(x<0) putchar('-'), x*=-1;
    if(x>=10) quickwrite(x/10);
    putchar(x%10+'0');
}
#else 
#include <iostream>
#endif
#include <algorithm>
using namespace std;
#define DEBUG
const int N=1e6+10;
int n;
struct Node
{
    int l, r; //0为空指针
}tree[N];

void init()
{
    read(n);
    for(int i=1; i<=n; i++)
    {
        int l, r;
        read(l), read(r);
        tree[i]={l, r};
    }
}

int GetHeight(int u)
{
    if(u==0) return 0; //当前是空节点
    int lh=0, rh=0;
    if(tree[u].l!=0) lh=GetHeight(tree[u].l);
    if(tree[u].r!=0) rh=GetHeight(tree[u].r);
    // printf("u:[%d]:%d\nl:[%d]:%d\nr:[%d]:%d\n\n", u, max(lh, rh)+1, tree[u].l, lh, tree[u].r, rh);
    return max(lh, rh)+1;

}

void solve()
{
    init();
    quickwrite(GetHeight(1)); puts("");
}

// #undef DEBUG
signed main()
{
    #ifdef DEBUG
        freopen("./in.txt", "r", stdin);
        freopen("./out.txt", "w", stdout);
    #endif
    #ifndef quickread
    ios::sync_with_stdio(0);
    cin.tie(0); cout.tie(0);
    #endif

    int T=1; //scanf("%d", &T);
    while(T--) 
    {
        solve();
    }
    return 0;
}
